Manifold and swivel connections for servicing multiple wells and method of using same

ABSTRACT

A system and method is provided for maintaining a live bore throughout a manifold while alternating between fluid flow to a stimulated wellbore and to an inactive or resting wellbore. At least two fluid inlets deliver fluid to the live bore, the fluid inlets straddling the two or more fluid outlets connected to the respective wellbores. One or more or all of the inlets or outlets can have multiple flow-impinging ports for reducing fluid velocity through each port. In another embodiment a method flushing system is provided for freeze protection for piping for a resting wellbore. Further, high fluid flow swivel connections between the manifold and wellheads simplify installation and reduce operational stresses.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Patent application Ser. No. 62/438,145, filed Dec. 22, 2016 and U.S. Provisional Patent application Ser. No. 62/561,842, filed Sep. 22, 2017, the entirety of which are incorporated herein by reference.

FIELD

Embodiments disclosed herein generally relate to servicing multiple wells with a fluid and, more particularly, to a system and method of flowing fluids through manifolds and wellhead assemblies to minimize the erosive effects of stimulation fluids and operational difficulties associated with dead zones in components and piping.

BACKGROUND

There are an increasing number of subterranean hydrocarbon reservoirs which are accessed using multiple wells for optimizing production therefrom. The wells and wellheads connected thereto are often closely spaced, the wellbores being angled downwardly and radially outwardly from a central location, such as a pad, to access as much of the reservoir as possible.

Many or all of the multiple pay zones in such reservoirs may be characterized by low permeability or other characteristics which require stimulation of one or more of the wells for increasing production therefrom. During selective stimulation of the wells, which may include fracturing operations performed on one well (an “active” well), wireline operations may be also be performed on other wells (“resting” wells), such as to shift wellbore access from one zone of the well to another. To consolidate pumping equipment, such as fluid pumpers and sand supply for use in fracturing, it is known to employ a large common manifold to selectively connect a source of fracturing fluid to one or more of the wellheads of the multiple wells. Thus, multiple wells can be stimulated from a common manifold or trains of multiple manifolds. Herein frac piping includes the manifold, fluid lines to the manifold, and frac lines from the manifold to the well. Further, while various proppants are known, a common proppant is sand, and herein the term sand is used as shorthand for all proppants.

To facilitate well stimulation operations on a multiple-well reservoir, a method called “zipper manifold fracking” is often used. In a typical zipper manifold fracking configuration, multiple wells are typically connected to a fracturing fluid pumper through a manifold and an active well is stimulated while a resting well is being maintained. During fracturing operations, the manifold is actuated to fluidly connect a first well W1 to the pumper while the remaining wells W2 . . . Wn are isolated therefrom.

The first well W1 is stimulated at a selected stage or zone, usually starting at the first stage. After stimulation, the manifold valves are actuated to isolate the first well W1 and fluidly connect the second well W2 to the pumper for stimulation of its designated stage, which is typically also its first stage. While the second well W2 is being stimulated, the first well W1 can be maintained, manipulated, or both. For example, a wireline can be run down the first well W1 to set a bridge plug and perforate the subsequent stage of the first well W1 to prepare it for stimulation. After stimulation operations are complete at the designated stage of the second well W2, the second well is isolated and the first well W1 is once again fluidly connected to the pumper for stimulation operations on a subsequent stage of the first well. In the meantime, a wireline can be run down the second well W2 to set the bridge plug, and perforate the second stage of the second well. Wells W3 through Wn can be similarly inserted into the operation. Such operations continue until all desired stages are stimulated in all desired wells.

As shown in FIGS. 1A, 1B and 1C, a conventional manifold 10 is provided, used for fracking multiple-well reservoirs. The manifold, typically receives the entirely of the fracturing fluid F, from frac fluid source 12, at an inlet 11 mid-point along the manifold 10. Fluid outlets to the wells are spaced along the manifold in both directions from the inlet. The frac fluid F typically travels in a first direction to the outlet for one or more wells, for example well W1, as shown in FIGS. 1A and 1B, and then, per operations, flow is switched to travel in a second direction to one or more other wells, such as well W2, shown in FIG. 1C. The conventional single operations, as described, result in localized high velocities of sand laden fluids and alternating stagnant areas of the manifold.

The erosive nature of the stimulation fluids F necessitates regular manifold maintenance. Stimulation fluids F typically have high fluid flow rates and flow velocity, and are conventionally directed around right angle corners of manifold fittings and other components, resulting in significant wear to the manifold, manifold valves, as well as to downstream equipment. Sand in the fracturing fluids further exacerbates erosive effects.

It is known to stockpile replacement manifold components onsite, including new flow blocks and valves, for replacing damaged and eroded components as the job proceeds. It is also known to have redundant fluid pumpers on standby, the redundancy required to maintain simultaneous and continuous stimulation despite the increased costs.

With reference to FIGS. 1B and 1C, in a further disadvantage, the conventional fluid flow path to the active well bypasses other unused areas of the manifold, those unused areas being temporarily dead ended or stagnant. Sand in the current fluid flow can encroach and accumulate in such stagnant areas. When operations switch to the next well and fluid is directed through the recently stagnant areas, the fluid can inject a slug of accumulated sand downstream to the wellhead and downhole into the well. Such slugs of sand have been known to damage equipment and/or obstruct the wellbore stage being stimulated.

Further, in cold weather environments, freezing can become a problem during such intermittent fracking operations, as residual water-based fluid can freeze in the stagnant areas of the frac piping including the manifold itself, fracturing stack, and various fluid lines when a well is resting in between fracturing stages. As it can take hours for stimulation operations to complete in the active well, fluid in the resting wells has ample time to freeze in cold conditions.

To mitigate freezing, it is conventional to wrap heat tracing such as insulated hot glycol or steam heating hoses around the various frac piping and the like to warm the components and fluid therein. However, the installation and use of heating hoses is time consuming, costly and, should the heater or heating hoses fail, the entire system could freeze before failure is detected, necessitating costly repairs and downtime. Typically, installing heating hoses around a manifold, fracturing stacks, and other components can take several days. Additionally, as the heat source is typically a boiler, a failure of the boiler compromises the entire heating system. Further still, boilers for heating systems are often controlled remotely, which adds to the risk of delayed detection failures by personnel.

The manifold is typically connected to the fracturing stacks of the multiple wells with one or more frac lines. The tortuous path of the lines between a manifold and the multiple uniquely spaced wellhead locations present various challenges, such as a multiplicity of connections and difficulty of secure installation in the tightly-spaced, and oft-times elevated environments of common wellhead equipment configurations.

The manifold are typically at ground level and the wellhead connections elevated. Some operators have chosen to employ single, continuous frac lines with right angle connections to connect a manifold fluid outlet to each of multiple fracturing stacks, Unitary, rigid welded lines are efficient in terms of minimizing connections. However, such unitary connection lines require precision in order to align and connect to components and other lines. In some instances, surveying is required to ensure alignment. Additionally, such lines are extremely rigid and unable to adequately absorb line jack and vibration, which can result in excessive stress on the fracturing stack connections, transference of vibrations from the manifold to the fracturing stack and vice versa, and otherwise contributing to an unsafe environment. Further, such lines are subject to substantial erosion and the unitary line must then be replaced as a whole as opposed to replacing only worn sections.

To address deficiencies associated with unitary continuous lines, some connections in the prior art have utilized swivel joints. Such joints are characterized by Chiksan® swivels and quick release, wing union terminating connections as shown in prior art FIG. 7. While convenient for quick connection and disconnect, the nature of the threaded, wing-union connections result in several deficiencies including: localized bore diameter reduction at the swivel connections with resultant increased erosive velocities, introduction of a structural weak point, difficulty in assembly of the male thread and female wing portions if misaligned, and troubles associated with the seal.

The wing union implements rubber seals that can be damaged by misalignment and in cases, be dislodged into the bore, and accidental transport down the well with the attendant difficulties downhole. Further seal loss results in high pressure leakage at surface, the severity of which can require pumper shut down and a generally unsafe environment. Further, assembly wing-union connections require hammering to secure which is difficult in tightly spaced and elevated locations.

The pressures and volumes of high pressure frac fluids in well stimulation place equipment and personnel at risk. There is a continuing need in the industry for a method to minimize erosion in the manifold and related frac piping, and to minimize stagnant areas with the associated sand accumulation and risk of freezing during down periods and between cycles.

Further, there is a need for a system and method to easily connect and disconnect a manifold with wellheads that avoids imposing local velocity increases, accepts pine movement and minimizes seal issues.

SUMMARY

Embodiments herein are directed to an apparatus, system, and method of selectively stimulating two or more wells from at least one common fluid source using one or more common manifolds, each manifold servicing one or more wells. A fluid, such as a fracturing fluid, is pumped from pumping units through the one or more manifolds to selected wells of the one or more wells. Manifold piping includes the manifold, fluid lines to the manifold, and frac lines from the manifold.

Herein, fracturing fluid is provided to a live bore of a manifold at inlets located at each of two or more extremities of the manifold, typically at each of the opposing ends of a linear manifold. One or more fluid outlets connect to the fracturing stacks of the one or more wells are located intermediate the inlets located at the extremities of the manifold. Thus, fluid is always flowing in all portions of the live bore regardless of the selected well, thereby avoiding dead areas for sand and other solids to accumulate. Further, velocity of the fluid is reduced along a majority of the manifold as the fluid rate at the inlets is reduced to at least one half as the fluid supply is split between two inlets rather than only flowing through one.

Hence, a nominal 100 units of flow, previously supplied to one inlet in the prior art, is now supplied to at least two inlets, having independent flows of 50 units each. In addition to the flow velocity being reduced by splitting the fluid supply to the manifold into at least two fluid streams, velocity and energy are further reduced as the streams converge within the manifold and impinge on one another as they meet and turn at right angles to flow out of a manifold outlet to a selected well. In embodiments, inlets can be arranged in opposing pairs such that fluid streams entering the manifold through opposing inlets impinge on one another to provide further velocity reduction. Additional velocity reduction can be achieved by sizing the inner diameter of the inlet ports to provide a total cross-sectional area smaller than that of the cross-sectional area of the live bore, and sizing the inner diameter of the outlet ports to provide a total cross-sectional area larger than that of the live bore. Such fluid stream management, in the form of both reduction of fluid velocity and energy reduction through impingement and bore sizing, mitigates the erosive effects of the stimulation fluid on the manifold and components downstream.

Simultaneously introducing fluid from opposing ends of a manifold maintains substantially the entirety of the manifold live so as to avoid dead areas and buildup of sand, and keeps the manifold warm, mitigating freezing of fluid within the manifold.

In one aspect, a system for delivering fluid from a common fluid source to two or more wellheads is provided, comprising: a manifold having an bore and two or more fluid outlets in communication with the bore and forming a live bore at least between the two or more fluid outlets, each fluid outlet being connected to a corresponding wellhead of the two or more wellheads and having a respective outlet valve between the live bore and the corresponding wellhead, the respective outlet valves being operable to deliver fluid to one wellhead at a time. Further, the manifold comprises at least first and second fluid inlets straddling the live bore and connected to the fluid source, wherein when one fluid outlet and wellhead is blocked at its respective outlet valve, fluid is delivered to another of the two or more wellheads through the entire live bore supplied from each of the at least first and second fluid inlets.

In another embodiment, cyclical operation is protected for the lines between the manifold and the staged wells as the operation to each well alternates or cycles between an active and resting well status.

In embodiments, a methanol tank and pump can be fluidly connected to the manifold to flush the manifold and the fracturing stacks of one or more resting wells with methanol to mitigate and prevent freezing of fluid therein.

In another embodiment, a method is provided for delivering methanol from a methanol source to a manifold and one or more fracturing stacks of one or more wellbores. The wellhead is isolated from the wellbore and a first fluid outlet of the manifold and an inlet valve of a selected fracturing stack are opened to flow fluid between the manifold and the selected fracturing stack. A return valve is actuated at the fracturing stack to flow fluid between the selected fracturing stack and the methanol source and methanol is circulated from the methanol source to the manifold, selected fracturing stack, and back to the methanol source.

In embodiments, one or more flanged swivel joints can be used to connect fracturing lines between the manifold and the fracturing stacks of the multiple wells. The flanged swivel joints can have uniform diameter through bores to avoid local velocity increases and employ durable ring seals to minimize the risk of seals being lost during connection or disconnection of the swivel joint. The flanged swivels enable secure line connection regardless of the landscape, manifold and wellhead alignments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic representation of a prior art manifold system;

FIG. 1B is a schematic representation of a supply of 100 units of frac flow to a first well using a prior art manifold system;

FIG. 1C is a schematic representation of a supply of 100 units of frac flow to a second well using the prior art manifold system of FIG. 1B;

FIG. 2A is a longitudinal partial cross-sectional view of an embodiment of a manifold system described herein, illustrating a common contiguous live bore header and a plurality of outlets fluidly connected thereto for controlled delivery fluid to multiple wellheads. A flow path is shown for delivery of fracturing fluid through the manifold to a first well;

FIG. 2B is a schematic representation of a supply of 100 units of frac flow to a first well, supplying 50 units from each of two opposing ends of a linear header or manifold;

FIG. 2C is a schematic representation of a supply of 100 units of frac flow to a second well, supplying 50 units from each of two opposing ends of the manifold;

FIG. 3A is a schematic representation of the relative fluid velocities at the inlets, outlets and live bore, wherein one half of the frac fluid is provided at each of the two ends of the live bore, the selected fluid outlet receiving the total flow for discharge to the sleeved well, but having two outlet ports, each outlet port discharging ½ of the total flow;

FIGS. 3B1 through 3B4 respectively are isometric representations of the management of various fluid flow options for the schematic of FIG. 3B, namely:

FIG. 3B1 illustrates an embodiment in which each inlet has one port for providing ½ of the total flow and the fluid outlet has two outlet ports for discharging ½ of the total flow;

FIG. 3B2 illustrates an embodiment in which one half of the frac fluid is provided at each end of two ends of the live bore, one of two inlets providing one inlet port for ½ of the total flow and the second inlet having three inlet ports, each providing ⅙ of the total flow, the second inlet totaling ½ of the total flow;

FIG. 3B3 illustrates an embodiment in which one half of the frac fluid is provided at each end of two ends of the live bore, each of the two inlets have three inlet ports for ⅙ for the total flow at each port combining to total ½ of the total flow at each inlet;

FIG. 3B4 illustrates an embodiment in which each inlet has one port for providing ½ of the total flow, and wherein the fluid outlet has four outlet ports, each of which discharges ¼ of the total flow;

FIG. 4 is a cross-sectional view of a block of the fluid inlet of FIG. 2A, illustrating inlets for receiving from a fluid source;

FIG. 5 is a cross-sectional view of a block of the fluid outlet of FIG. 2A, illustrating outlets for fluidly connecting to a wellhead;

FIG. 6A is a schematic representation of an embodiment of a methanol flushing system for flushing the manifold and wellhead components, such as those of FIG. 2A, with the manifold configured to circulate methanol from a source, through an intermediate fluid outlet to a first resting well and back to the source;

FIG. 6B is a schematic representation of the methanol flushing system of FIG. 6A with the manifold configured to flow methanol through an intermediate fluid outlet to a second resting well;

FIG. 6C is a schematic representation of an embodiment of a methanol flushing system for flushing the manifold and wellhead components, with the manifold configured to flow methanol through an fluid outlet in fluid communication with a respective fracturing stack;

FIG. 7 is a flow diagram setting out an example process for flushing a manifold system and wellhead components with methanol;

FIG. 8 illustrates a prior art Chiksan® swivel connection with quick release wing union connections;

FIG. 9 is a cross-sectional view of a swivel connection with flanged connections according to one embodiment;

FIG. 10A is a perspective view of the connections between a manifold and two fracturing stacks employing swivel connections, each stack having two fracturing lines connecting the stack to the manifold;

FIG. 10B is an alternative perspective view of the connections between a manifold and fracturing stacks of FIG. 9A;

FIG. 11 is a perspective view of the connections between a manifold and two fracturing stacks having an alternative swivel configuration; and

FIG. 12 is a perspective view of a fracturing stack having swivel connections to fluidly connect the fracturing stacks and the manifold.

DESCRIPTION

Embodiments of a manifold and system for fracturing multiple wells, and maintenance thereof, are described herein. Embodiments described herein are suitable for delivery of a variety of stimulating fluids, but are generally described in the context of the flow of fracturing fluid in a fracturing operation. Particular advantages are obtained when using embodiments of the invention for delivering water-based fracturing fluids F which further carry a particulate sand P therein. References to sand P include sand and other proppant typically used in well stimulation operations.

With reference to FIG. 2A, in an embodiment, a manifold 10 receives frac fluid from a source 12, the manifold comprising an axial bore 34 formed therethrough. Fluid outlets 40 are spaced along the manifold and each outlet 40 can have one or more outlet ports 44 thereabout for fluid communication of frac fluid F between the bore 34 and wells W. A fluid outlet 40 is assigned to each well and outlet valves 48 can be positioned adjacent each of the ports 44 of each outlet 40 for selectable discharge of frac fluid F therefrom. In this manner, each well W1,W2 . . . is independently connected to the live bore 34 with a respective fluid outlet 40,40 . . . for individually operation or fluid isolation from the live bore.

Two or more fluid inlets 30,30 are located on the manifold 10. Each fluid inlet 30 can have one or more inlet ports 38 for fluid communication of frac fluid F between the source 12 and the between the bore 34. The fluid inlets 30,30 bookend or straddle all the fluid outlets 40,40 . . . forming a live bore therebetween. In operation, the fluid path from any fluid inlet 30 to the furthest fluid outlet 40, passes every other fluid outlet, so that the entirely of the manifold bore 34 between the fluid inlets 30,30 has fluid flowing therein regardless of which well is under stimulation. Inlet valves 39 can be positioned adjacent each of the inlet ports 38 selectably permitting frac fluid F from the source 12 to flow therethrough into the manifold 10.

As shown, in this embodiment, one of the inlet ports 38 of each fluid inlet 30,30 is in-line with axial bore 34 of the manifold 10.

The improved manifold 10 provides fluid flow through the entire manifold bore 34 regardless of which well W is currently active. The bore 34 is live and therefore absent stagnant areas. The live bore 34 prevents accumulation of sand P between the fluid inlet and fluid outlet to an offline well, and further mitigates freezing therein.

Additionally, the velocity of fluid F entering and exiting the bore 34 can be reduced by fluid inlet 30 and fluid outlet 40 management including strategically sizing and orientation of inlet ports 38 and outlet ports 44, and selecting the numbers of ports active on any particular fluid inlet or outlet 30,40. Erosive effects of the frac fluid F can be minimized at the manifold and attached manifold piping as described in greater detail below.

As stated above, the manifold 10 can comprise two or more fluid inlets 30 located at least at opposing ends 36,36 of the manifold bore 34. The manifold comprises plurality of spools 52 fluidly connecting the fluid inlets 30 and outlets 40 to form the continuous bore 34. With reference also to FIG. 4, each of the fluid inlets 30 has a intersected bore 32 in communication with the live bore 34 and each of the multiple inlet ports 38 extending radially therefrom. With reference also to FIG. 5 each of the fluid outlets 40 have an intersected bore 42 formed in communication with the live bore 34 and each of the multiple outlet ports 44 extending radially therefrom. Each of the connectors 52 have a connector bore formed longitudinally therethrough which is contiguous with the inlet intersected bore 32 and outlet intersected bore to form the continuous live bore 34. Connections between fluid inlets 40, fluid outlets 46, connectors 52, inlet valves 39, and outlet valves 48 can be flanged connections or any other connection means known in the art for fluidly connecting components.

While the manifold 10 is comprised of various modular, discrete components as described herein, one of skill in the art would understand that manifold 10 can comprise a mixture of fastened and unitary components, such as welded and bolted configurations.

Continuous Flow and Flow Impingement

Returning to FIG. 2A and schematics of FIGS. 2B and 2C, fluid F is supplied to the inlets 30,30 located at the outboard ends of the two or more fluid outlets 40,40 of the manifold 10. In this embodiment, the inlets 30,30 straddle the fluid outlets 40,40, shown here to be opposing terminal ends 36,36 of the manifold.

Thus, and with reference to FIGS. 2B and 3A, frac fluid F traverses the manifold 10 from both ends thereof. For stimulation of a first well W1 with 100 units of frac fluid, 50 units of fluid are provided through first inlet and 50 units are provided through the other, opposing ends of the live bore. The entire live bore of the manifold is traversed and no stagnant areas result, regardless of the inactive, or resting second well W2. With reference to FIG. 2B, for stimulation of the second well W3 with 100 units of frac fluid, 50 units of fluid are provided through first inlet and 50 units are provided through the other, opposing ends of the live bore. Again, the entire live bore of the manifold 10 is traversed and no stagnant areas result, regardless of the inactive, or resting first well W1.

Further, while avoiding stagnant areas in the bore, the erosive nature of the 100 units of frac fluid F(100) is reduced. The majority of the live bore 34 receives a reduced flow rate, reduced velocity and reduced erosive effects. As two opposing streams of frac flow F(50),F(50) converge at the fluid outlet 40, each frac flow F(50) through the fluid inlets 30 is one half the total full frac fluid flow rate F(100) being supplied to the manifold 10. As described below, further mitigation of erosion is accomplished with multiple inlet ports 38 and multiple outlet ports 44.

As the number of inlet ports increases, the volumetric rate and velocity of each stream is inversely proportional to the number of inlets 38. For example, as shown in FIG. 2A, fluid F enters manifold 10 at two fluid inlets 30 of three inlet ports 38,38,38 each, for six inlet ports total 38. Therefore, there are six initial fluid streams into the manifold 10, the flow rate of each stream is about ⅙ of the total fluid flow rate. The three streams of each fluid inlet 30 converge in the intersecting bore 42 30 to form a fluid streams having about ½ the total fluid flow rate and travelling at about ½ the flow velocity compared to a single stream. If a third fluid inlet 40 were introduced, such as being located intermediate along the manifold, then three fluid streams would be formed in the live bore 34, each at about ⅓ the total fluid flow rate and velocity.

As shown in FIGS. 2A, 2B and 2C, even if frac fluid F is directed to a first well W1 supplied by one or more fluid outlets 40 adjacent one end of the manifold 10, the remainder of the live bore 34 continues to receive a flow of fluid F, thus avoiding deposition and accumulation of sand and other solids in any part of the live bore 34, having general eliminated stagnant or dead flow areas of any significance. Further, the velocity of the fracturing fluid F as it travels along the live bore 34 is about one-half the velocity of fluid flowing through the of the conventional manifold system 10 of FIGS. 1A to 1C, thereby reducing the erosive effects of fluid flow on the manifold 10 and other components.

In the fluid inlet 30, the three streams from ports 38,38,38 converge in the intersecting bore 32 and impinge on each other. Such impingement reduces further reduces fluid velocity and dissipates energy to mitigate erosion of the components of the manifold 10. Similarly, the streams from the opposing fluid inlets converge at the fluid outlet 40 before discharge through the outlet ports 44,44 . . . the opposing streams impinging and reducing the erosive energy.

In a preferred embodiment, as best shown in FIG. 4, some or all of the inlet ports 38 are formed in fluid inlets 40 in opposing pairs such that the fluid streams entering through the opposing inlet ports 38,38 impinge on one another as they enter the live bore 34 to further reduce flow velocity and dissipate energy. In the depicted embodiment, each fluid inlet 40 has four inlets 38 positioned in an opposing arrangement and an additional fifth inlet 38 is oriented in-line with the longitudinal live bore 34. The reduction in velocity and energy caused by the impinging fluid streams further aids in reducing the erosive effects of the fracturing fluid F within the manifold 10 and downstream equipment.

By having multiple inlets 38 and outlets 44 formed in each fluid inlet 40 and fluid outlet 46, respectively, some or all of the inlet and outlet valves 39,48 can be placed out of axial alignment with the manifold's live bore 34, allowing easier access thereto for maintenance, repair, or replacement. This is particularly advantageous when the stimulation fluid F is a frac fluid carrying sand, which is highly erosive at high velocity. Further, by strategically sizing the inlets 38, outlets 44, and live bore 34 as described in detail below, the valves 39,48 and other components of the manifold 10 are subjected to lower velocity flows, reducing wear and erosion.

The sixing of the various flow paths can further reduce the erosive effects. Returning to FIG. 4 and with reference to FIG. 5, the inner diameter and cross-sectional area IBXA of the fluid inlet 30, the cross-sectional area OBXA of the fluid outlet 40, and cross-sectional areas CXA of the connectors 52 are substantially equal to and corresponds to the diameter and cross-sectional area LBXA of the live bore 34. Thus, the live bore cross-sectional LBXA=IBXA=OBXA=CXA which minimizes flow various and erosion as fluid F flows through the live bore 34.

The bore 42 of the fluid inlet 42 can have an internal diameter IBID defining a total cross-sectional area IBXA. Each of the one or more inlet ports 38 can have an internal diameter IID, defining an inlet cross-sectional area IXA. The cross-sectional area IBXA of the fluid inlet coupled to the live bore is preferably greater than the total combined inlet cross-sectional area TIXA of the inlet ports 38 for reducing the velocity of the frac fluid F entering the fluid inlet 30. Accordingly, as the frac fluid F travels from the relatively smaller total inlet cross-sectional area TIXA into the relatively larger live bore cross-sectional area LBXA, the velocity of the fracturing fluid F decreases.

With reference to FIG. 5, the intersecting bore 42 of the fluid outlet 40 can have an internal diameter OBID defining a cross-sectional area OBXA. Each of the one or more outlet ports 44 has an internal diameter OID defining an outlet cross-sectional area OXA. A total combined outlet cross-sectional area TOXA of the outlet ports 44 is preferably greater than the cross-sectional area OBXA. Accordingly, as the frac fluid F travels from the relatively smaller cross-sectional area OBXA of the fluid outlet bore 42, into the relatively larger total outlet cross-sectional area TOXA, the velocity of the fracturing fluid F is further decreased.

As above, the sizes of inlet ports 38, outlet ports 44, and the size of the live bore 34 can be selected to strategically reduce the velocity of fluid F flowing therethrough. Further, in embodiments the numbers of inlet ports 38 and outlet ports 44 similarly impact fluid velocities. As shown in FIG. 3B1, two opposing fluid inlets each provide ½ of the nominal flow of frac fluid, whilst two opposing outlet ports each similarly discharge ½ of the nominal flow of frac fluid, combining downstream to deliver the entire total frac fluid to the well. As shown in FIG. 3B2, simply by a first fluid inlet provides ½ of the total flow and the second inlet is fit with three inlet ports, each providing ⅙ of the total flow totaling ½ of the total flow, whilst two opposing outlet ports each similarly discharge ½ of the nominal flow of frac fluid, combining downstream to deliver the entire total frac fluid to the well. In FIG. 3B3 each of two fluid inlets have three inlet ports, for providing ⅙ of the total flow at each port. Again, two opposing outlet ports each similarly discharge ½ of the nominal flow of frac fluid, combining downstream to deliver the entire total frac fluid to the well. In yet another embodiment, illustrating effect of the fluid outlet, an embodiment is shown in which each fluid inlet has one inlet port, each of which provides ½ of the total flow; however, the fluid outlet is fit with four outlet ports, each of which discharges ¼ of the total flow for combination downstream.

The strategic reduction in velocity of the frac fluid F at key locations greatly reduces the erosive effects on the manifold 10 and downstream equipment. As an added benefit, the smaller individual outlets 44 can have smaller corresponding valves 48, which are less expensive, and easier to remove for repair or replacement.

Methanol Flush

As above, the bore of the entire manifold remains live, regardless of which well is being stimulated and which is resting. Further, a method is described herein for mitigating freezing of fluids in fracturing lines extending from the manifold 10 to the wellheads or fracturing stacks of a resting well W.

With reference to FIGS. 6A, 6B and 6C, in embodiments, a methanol-containing fluid M can be circulated through manifold 10 and connecting fracturing lines 21 to select fracturing stacks 20 of wellbores W to prevent the freezing of fluid F therein when a well is in a resting state.

In more detail a tank 60, from a source of methanol of tank 60 containing methanol M, can be fluidly connected to one or more inlet ports 38 of manifold 10. One or more pumps 62 can be fluidly connected to the tank 60 to deliver methanol M to the manifold 10, select fracturing stacks 20, and back into tank 60. Preferably, the methanol tank 60 is fluidly connected to the fluid inlets 30,30 located at the opposing end of the manifold 10 such that the entire manifold live bore 34 is exposed to the methanol M regardless of which fracturing stack 20 is selected for flushing.

Fracturing stacks 20 each have at least one stack inlet 22 in communication with at least one respective outlet port 44 of the manifold 10 via one or more fracturing lines 21. Each inlet can have a corresponding adjacent gate valve 24 for permitting fluid to flow therethrough. Fracturing stacks 20 can further comprise an axial bore 23 in communication with the stack inlets 22 and generally in-line with the wellbore W. One or more return lines 64 connect the axial bore 23 of each of the frac stacks 20 and the methanol tank 60, and one or more fluid return valves 66 can be located adjacent the stack 20 for selectably permitting flow of methanol M from the axial bore 23 back to the methanol tank 60. A wellhead valve 29 is located between each of the fracturing stacks 20 and their respective wellbores W for selectably isolating the axial bore 23 from the wellbore W.

During methanol flushing operations, the return valve 66 of the frac stack 20 to be flushed is in the open position and the wellhead valve 29 is in the closed position, such that methanol M flows back to the tank 60 via return line 64 instead of into the wellbore W. In the embodiments depicted in FIGS. 6A-6C, the fracturing stacks 20 each have multiple inlets, two inlets 22,22 shown.

In an embodiment, and as shown in in the schematics of FIG. 6A and flow chart of FIG. 7, a process 100 for flushing a manifold 10 connected to a plurality of fracturing stacks 20 with methanol M is now described. The outlet valves 48 of the manifold 10 can be actuated to direct fluid to a first fracturing stack 20 a to be flushed (step 102). The return valve 66 of fracturing stack 20 a is actuated to the open position, and the wellhead valve 29 is actuated to the closed position (step 104). In embodiments where fracturing stacks 20 have more than one fracturing stack inlet 22, methanol M is preferably flowed through each fracturing stack inlet 22 individually. Thus, a first gate valve 24 of a first inlet 22 of frac stack 20 a is actuated to the open position to receive methanol M while all other gate valves 24 remain closed (step 106). Methanol M can then be pumped through the inlets 38 of manifold 10 and subsequently flow through the one or more outlets 44 corresponding with fracturing stack 20 a (step 108). After exiting the manifold 10, methanol M continues through fracturing line 21 to the selected fracturing stack 20 a. Methanol M flows into frac stack 20 a through first inlet 22 into axial bore 23, and subsequently is circulated back to methanol tank 60 via return line 64.

After flushing through the first inlet 22 is completed, the gate valve 24 corresponding to the first fracturing stack inlet 22 is closed and, if there are subsequent inlets 22 to flush (step 110), the gate valve 24 corresponding to a subsequent stack inlet 22 is opened for flushing thereof (step 112). Such sequential flushing of stack inlets 22 continues until all of the gates 24 and inlets 22 of the fracturing stack 20 a have been flushed. This sequential flushing provides a more thorough exposure of the components of the fracturing stack 20 to the methanol M.

Once methanol flushing on first fracturing stack 20 a is completed, return valve 66 and all other valves of the fracturing stack are closed (step 114) and other operations, such as wireline or stimulation operations, can be performed on the stack. The methanol M remaining in the manifold 10 and flushed frac stack 20 a can be shut in to keep the lines filled with methanol M and ready for the next stimulation or other process. In this manner, methanol M de-ices and mitigates freezing of residual fluid inside the manifold 10, fracturing lines 21, fracturing stack 20 a, and other components.

If it is desired to flush subsequent fracturing stacks 20 (step 116), and as shown in FIG. 6B, manifold 10 can be actuated to fluidly connect the fracturing stack of a subsequent well, such as second stack 20 b, to methanol tank 60, and the return valve and wellhead valve of fracturing stack 20 b can be actuated to the open and closed positions, respectively (step 120). The flushing process can then be performed again for the new stack 20 b. The methanol flushing process can be repeated until the fracturing stacks 20 of all desired wells W have been flushed.

Wellhead valve 29 and other lines and equipment therebelow are not exposed to methanol M. As such components are typically near the relatively warmer ground area, one can conservatively install conventional heating around those components for freezing protection.

In the context of a multi-well fracturing operation, methanol flushing can occur at a well W when it is undergoing maintenance and before wireline operations (e.g. installation of a bridge plug and perforation). For example, in a zipper manifold fracturing operation, wherein an “active” well is stimulated while a “resting well” undergoes maintenance and preparation for a subsequent stimulation stage, the resting well can first be flushed with methanol M for the hours need for stimulation of the active well.

Preferably, a source of methanol M in tank 60 initially comprises 100% methanol to permit dilution by the water-based fluids returned to the tank 60 over a series of flushing operations, and is maintained at a concentration of about 40% methanol and preferably above 50% methanol when ambient temperatures are −25° C. or below.

Preferably, before methanol flushing operations begin, sand-laden frac fluid is flushed out of the various supply lines with sand-free frac fluid, otherwise sand may be carried into the methanol tank 60 along with the flushed frac fluid. Tank 60 can be fit with a screen 63 to filter out solids entrained in the methanol M as the fluid is being pumped out, a sump 61 for allowing finer particulates to settle therein, or both. Additionally, methanol M can be drawn from a point in the tank 60 high enough such that solids settled in the sump 61 will not be pumped to the manifold 10 or components downstream. The tank 60 can be cleaned to remove solids on a regular basis, for example at the same time the methanol M is replenished.

Methanol pump 62 or pumps can be conventional, such as an impeller pump capable of flowing methanol M at a rate of 100 gallons/min at about 100 psig.

As one skilled in the art would understand, multiple manifolds 10 can be used in conjunction in order to service more wells W. Fluid lines used for the methanol flushing system can be hydraulic hoses rated for 200-300 psi, with the view of being durable and easy to move.

Swivel Joint

Flanged swivel joints 70 can be employed in the system at various locations along the fracturing lines 21 connecting the manifold 10 and the fracturing stacks 20. Such flanged swivels 70 further mitigate leaks, ingestion of seals and localized velocity increases, as sections of reduced bore diameter present in conventional swivel joints having wing-union connections are absent. As shown in FIG. 9, the swivel comprises two 90 degrees sections, each section having a distal end terminating at a circumferential distal swivel and a flange, and the proximal ends connected at a proximal swivel for providing a U-shaped fitting infinitely rotatable 360 degrees at the proximal swivel. The swivel can be U-shaped with the distal flanges parallel and aligned in the same plane, through 90 degrees with the flanges at 90 degrees to one another, and rotatable 180 of the 360 degrees to form an S-shape with the flanges parallel, the planes of which are spaced.

With reference to FIGS. 10A to 12, herein, embodiments of a flanged swivel joint 70, such as that of FIG. 9, provide a strong, safe and easily configured system for connection between a manifold 10 and a fracturing stack 20. Swivel joint 70 has flanged connections 72 at both ends for connection to various components and connection lines such as fracturing lines 21. By eliminating the unreliable and weak wing union connections of prior art swivel joints, as shown in the prior art swivel of FIG. 8, fittings can be specified and bore diameters can be strategically matched or varied relative to the bore diameters of upstream and downstream piping for reducing or maintaining local fluid velocities and avoiding resultant erosion hot spots. The use of flanged connections 72 also allow for larger inner bore diameters while maintaining similar outer diameter as the inlets to the fracturing stacks 20. In the prior wing union case a reduction of inner bore diameter is required near the connecting ends to accommodate the wing. The relatively increased bore diameter of the flanged swivel 70 allows a lower flow velocity to achieve the same rate of flow.

For example, the inside diameter of a prior art nominal 4″ inner-diameter Weco 1502 swivel joint has an inner-diameter of about 3.25 or 3.5″ near the connecting ends, which allows a 6 m³/min flow rate at 52 fps. However, a same-diameter nominal 4″ flanged swivel joint 70, with the larger inside diameter, is able to maintain the same flow rate at a velocity of 40 fps throughout the joint, with no local velocity increases at the connecting ends. Increased capacity is available, while suffering the same erosive rate as the lower flow rate of the conventional swivels. Velocity in the flanged joint 70 can be increased to 52 fps to achieve a flow rate of 7.75 m³/min. The flanged swivel joint 70 is also easier to secure to connected components, as no hammering is required, and alignment with components can be achieved passively by swivel rotation while the flanges are cinched square to the connecting flange.

The flanged swivels 70 are manufactured with large enough bore diameters to maintain low flow velocity (preferably less than 50 feet per second) as the typical sand laden fracturing fluids F are pumped therethrough at high rates and for periods of time.

One or more swivel joints 70 can be implemented at each end of the connection between the fracturing stack 20 and manifold 10 to allow the connection line 21 to move in all directions and accommodate line jack movement and vibration for reducing introduced stresses on the substantially rigid fracturing stack 20 and connections including the connection lines 21 to the fixed manifold 10. Movement is accommodated by providing freedom of movement between the manifold and the fracturing stack 20

The flanged swivels 70 are connected to a block face or other flange of the conventional equipment, utilizing a conventional ring seal 74, such as a stainless steel ring gasket, that is much stronger and more reliable than wing union seals.

The flange connections 72 enable ease of installation with the connection line 21 and/or other components, even with initial misalignments, as the flanged connection 72 can cinched up with one or more bolts while the swivel 70 adjusts to force the line 21 into proper alignment. The stronger and leak-proof connections 72 enable providing connections of line 21 in combinations and arrangements including at least one swivel 70 at each end of the long line joint between the manifold 10 and fracturing stack 20.

Further, the security of the flanged connection 72 enables limiting wing swivel to a single swivel connection 70, additional degrees of freedom being provided by bolting flange-to-flange another intermediate swivel 70 for maximum angular flexibility.

As shown in FIGS. 9, 10A and 10B, for example a three-way swivel 70 a could mount between an elevated fracturing stack 20 and fracturing line connection 21 which extends to the manifold 10 typically at ground level. A second swivel 70 b can be located at the end of the long joint of line 21, on the ground, adjacent the manifold 10, and a third swivel 70 c can be located adjacent the manifold fluid outlet 40. The two joints 70 b and 70 c enable free longitudinal growth of line 21.

In a further embodiment, as shown in FIG. 11, additional swivel joints 70 d can be combined together with the fracturing stack swivel 70 a, and the fluid outlet swivels 70 b,70 c, to provide additional angular degree of freedom to fracturing line 21.

As a result of the high flexibility of the high pressure connections using the high-flow flanges swivels, a safe reliable fracturing system ins achieved that that includes higher reliability, longer periods between maintenance cycles and the ability to absorb jack and vibration. 

We claim:
 1. A system for delivering fluid from a common fluid source to two or more wellheads, comprising: a manifold having a bore; two or more fluid outlets in communication with the bore and forming a live bore at least between the two or more fluid outlets, each fluid outlet being connected to a corresponding wellhead of the two or more wellheads and having a respective outlet valve between the live bore and the corresponding wellhead, the respective outlet valves being operable to deliver fluid to one wellhead at a time; and at least first and second fluid inlets straddling the live bore and connected to the fluid source, wherein when one fluid outlet and wellhead is blocked at its respective outlet valve, fluid is delivered to another of the two or more wellheads through the entire live bore supplied from each of the at least first and second fluid inlets.
 2. The system of claim 1, wherein the bore is an axial bore and the at least first and second inlets are located adjacent opposing distal ends of the axial bore, the live bore being formed between the at least first and second inlets.
 3. The system of claim 1, wherein each fluid outlet has two or more outlet ports.
 4. The system of claim 1, wherein each fluid inlet has two or more inlet ports.
 5. The system of claim 4, wherein two or more inlet ports are opposing for impinging their respective flow of fluid.
 6. The system of claim 1, wherein: the at least first and second inlets are formed in respective first and second fluid inlets and in communication with an intersecting inlet bore of each of the first and second fluid inlets; each of the at least one fluid outlet is formed in a respective fluid outlet and in communication with an axial outlet bore of each of the fluid outlets; and the fluid inlet bore and fluid outlet bore are in fluid communication with each other and comprise at least a portion of the live bore.
 7. The system of claim 1, wherein the first inlet and second inlets each comprise at least one pair of opposing inlet ports.
 8. The system of claim 1, wherein each of the at least one fluid outlet comprises at least two outlet ports.
 9. The system of claim 1, wherein a sum of the cross-sectional flow area of the inlet ports of the at least first and second inlets is equal to or less than a cross-sectional flow area of the live bore.
 10. The system of claim 1, wherein a sum of the cross-sectional flow area of the outlet ports of each of the at least one fluid outlets is equal to or greater than the cross-sectional flow area of the live bore.
 11. The system of claim 1, further comprising a methanol source in fluid communication with the at least first and second inlets and configured to selectively deliver methanol to the live bore and selected wellheads, and receive returned methanol.
 12. The system of claim 11, wherein the methanol is maintained at a concentration of above 40% methanol.
 13. The system of claim 11, wherein the methanol source is fit with a sump to allow solids to settle therein and a screen to filter out solids from methanol being delivered to the live bore.
 14. A method of delivering a methanol from a methanol source to a manifold and one or more fracturing stacks of one or more wellbores, comprising: Isolating a selected fracturing stack from the wellbore; opening first fluid outlet of the manifold and a first stack inlet valve of a selected fracturing stack to permit fluid communication between the manifold and the selected fracturing stack; opening a return valve of the selected fracturing stack to permit fluid communication between the selected fracturing stack and the methanol source; and circulating the methanol from the methanol source to the manifold, selected fracturing stack, and back to the methanol source.
 15. The method of claim 14, further comprising: actuating the first fracturing stack inlet valve to the closed position and actuating a subsequent fracturing stack inlet valve of the selected fracturing stack to an open position; and circulating methanol through the subsequent stack inlet valve.
 16. The method of claim 14, wherein the step of pumping the methanol further comprising filtering solids from the methanol returning to the methanol source.
 17. The method of claim 14, further comprising maintaining the methanol mixture at a methanol concentration of at least 40%
 18. A system for fluidly connecting a manifold with one or more fracturing stacks of one or more wellbores, comprising a plurality of fracturing lines fluidly connecting a manifold to one or more fracturing stacks, wherein one or more of the plurality of fracturing lines comprises at least one flanged swivel joint, each of the at least one flanged swivel joint having first and second flanged connections an inside diameter corresponding with that of the manifold or fracturing stack.
 19. The system of claim 18, wherein the one or more swivels comprise at least three swivels. 